Bump shelljs from 0.7.8 to 0.8.5

Bumps [shelljs](https://github.com/shelljs/shelljs) from 0.7.8 to 0.8.5.
- [Release notes](https://github.com/shelljs/shelljs/releases)
- [Changelog](https://github.com/shelljs/shelljs/blob/master/CHANGELOG.md)
- [Commits](shelljs/shelljs@v0.7.8...v0.8.5)

---
updated-dependencies:
- dependency-name: shelljs
  dependency-type: direct:development
...

Signed-off-by: dependabot[bot] <support@github.com>

package.json

@@ -125,7 +125,7 @@
     "sass-loader": "^6.0.6",
     "selenium-server": "^3.7.0",
     "semver": "^5.4.1",
-    "shelljs": "^0.7.8",
+    "shelljs": "^0.8.5",
     "sinon": "^2.4.1",
     "sinon-chai": "^2.14.0",
     "swig": "1.4.2",